Woven brake lining, yarn, and process for making same



'Pa see fle 9" 1937 WOVEN BBAKELINING, YARN, AND PROC- ESS FOR MAKING SAME William meme, Clifton, N. J., assignor to World Bestos Corporation, Paterson, N. J2, a L corporation of Delaware No Drawing.

10 Claims.

This invention relates-to brake lining, the yarn forming the lining, and a process for making the same. The invention relates further to novel means for producing a smooth friction surface on 5. brake lining.

In brake lining, particularly as applied to automotive vehicles where a soft pressed steel drum is employed as a cooperating friction material, it is desirable that. thesurface of the lining have a 10 uniformly smooth surface so that the friction may be readily controlled and scoring of the steel prevented. a

'It is an object of the present invention to provide a brake lining wherein a smooth friction surface is produced with the addition of material to the brake lining of such small quantity as not to affect the balance of the frictional substances entering into the brake lining composition.

I It is another object of the'invention' to develop a novel process by means of which a powdered ingredient may be added to woven asbestos without creating impossible manufacturing conditions such as the production of excessive dust in the carding machine.

Another object of the invention is to provide a type of yarn which may be employed for various processes including woven brake lining and which a has the property of wearing with a smooth surface in contact with other frictional surfaces.

. Still another object of the invention is to provide-a surfacing material for brake linings, in gen.- eral and woven brake lining in particular which -maintains. a coefiicient of friction of desirable value throughout the high temperature ranges of brake lining use. I v 1 An additional objectis the provision of improved means for stabilizing the frictional resistance of the lining and preventing the dust worn from the lining from becoming abrasive.

40 Further objects of the invention will appear on consideration of the following specification of the invention in which apreferred process and product will be described.

Woven brake lining is commonly made from a 45 mixture of asbestos fibre and cotton fibre, the

asbestos having desirability on account of itslinear crystalline structure and resistance to heat,

and the cotton fibre because of its characteristics in insuring a unified texture to the yarn and 50 resulting fabric.

In the present process asbestos fibre is used of the type known in-the trade as spinning fibre having an average length of one-half inch. This asbestos is mixed with cotton fibre in a so-called mixing picker or cone willower of well known con- Application September 21, 1934,

Serial No. 744,941

struction, the apparatus including rotating rails of projecting teeth which mix and intertwine the fibrous contents of the cone.

After a thorough The silicate is of the type known commercially as Asbestene, a product containing by weight silica 61%, magnesium 31%, lime combined with silica 4%, and water of crystallization 4% and is distributed in granular form. The oxide also is in granular form. The silicate and oxide in the proportions of about 2 to 1 and the oxide forming between 0.20 %'to 5% of the weight of asbestos are mixed in a ball mill 0! the usual type and then the mixture is passed through a screen andadded to the cotton-asbestos mixture in the tumbling mill either before or after the introduction of these materials into the tumbling mill. The mill, which has an oversize capacity of approximately 60%, is operated until the oxide-silicate is finely distributed throughout the fibrous stock of cotton and asbestos, and the material is then passed into a carding machine where the usual sliver and roving is formed. The rovings which have a light pink color are then twisted into yarn with brass,

zinc, or lead wires, forming yarns which may be woven into brake lining.

The woven yarn before impregnation is composed of about 60% asbestos, 9% cotton and 30% metal such as brass, zinc or lead wires.

Various impregnants such as 40% by weight of overheated China-wood oil, 20'} synthetic resin consisting of cresylic acid and formaldehyde and 40% of coal tar solvent may be added to the woven lining and this impregnation is followed by a low temperature oven heat at about 200 F. to remove the solvent, succeededby further heat at a grad-..

ually rising temperature to approximately 390 F., which latter temperature is maintained for approximately one hour.

The lining is then removed and compressed or rolled'to the finished size, the'impregnant constituting about of the finished lining.

The completed lining therefore includes the component materials in approximately the following proportions and ranges:

. Percent Asbestos 52.17 Cotton 7.82 Metal 26.08 Iron oxide 0.13 Magnesium silicate 0.26 Impregnant 13.04

Percent 30 i-.060 4 to10 to 0.1 to 4 0.2to 8 10 to20 so small relatively, such means have been found necessary in order to insure the presence of the I iron ,oxide all through the brake lining. Howcentages, generally ranging from six to eight .ever, the magnesium silicate has utility in. the

brake liningin thatit is formed of smooth faced crystals which tend to break with sharp Jagged edges which assist in the frictional operation. The fine particles of the silicate, moreover, tend to form smooth flakes on the face of the lining and thus assist in building up a smooth surface.

However, it is the small percentage of iron oxide whichflproduces a most extraordinary effect in that by its operation a smooth, shiny friction surface develops on the brake lining which effectively maintains a uniformity of frictional resistance over wide temperature ranges. Temperatures of 600 to 700 F. are not unusiial in brake lining, and whereas in the case of brake linings including carbon black such temperatures will cause a drop-of the frictional resistance to as low as 0.1, in the case of iron oxide under similar temperature conditions the drop is no lower than 0.2.. In addition, the hardness.

ofthe iron oxide according to the Mohs scale is 2, whereas the hardness of the magnesium silicate is 1, and thus the silicate tends tofracture and yield under pressure, whereas the oxide has greater rigidity. If there was no iron oxide or its equivalent present the surface would become dull and dusty and the friction would become erratic.

Various substances other than iron oidde will produce the smooth glass like surface on the lining, such as carbon hereinabove mentioned, but these substances require muchhigher perpercent, and this large amount of added material produces excessive dust around the carding machine and interferes with the carding of the fibres. 0n the other hand, the small percentage of iron oxide and magnesiumsilicate causes praeticallyno dust around the carding machine and does not interferewith the carding of the fibres but on the contrary improves the carding operation. It is also 'notworthy that as the asbestos fibres wear away in the brake lining there is also a wearing away of-small particles of the iron oxide so that the smoothing effect in the composite dust particles is maintained and erratic brake action is prevented. Fiu'ther, the presence of theiron oxide seems to prevent a polishing of the surface of the steel drum which is undesirable in its relation to brake action.

v The useof iron oxide has been described with reference to woven brake lining but experiment has demonstrated its utility also in molded brake lining. 'The character of the oxide is such, in conjunction with asbestos and other friction materials, as to cause a smooth layer or surface on the wearing side of the lining irrespectiveof the type of bond employed.

and i'mpregnant 13%. i

, 9,100,847 'ihe purpose of the magnesium silicate in con- Modifications oithe composition and process other than those hereinabove mentioned may, of,

course. be made, and consequently I do not desire to limit myself to the preferred form of the invention except as required by the claims hereto appended.

Having thus described desire to claim is:

1. A yarn suitable for brake lining comprising asbestos and cotton fibres matted together and my invention, what I twisted with a reinforcing filament, and a powdered mixture containing iron oxide coating said fibres.

2. A yarn suitable for brake lining compris- I ing asbestos fibres coated with a powdered sub stance containing iron oxide and a supporting means for said asbestos.

3. A yarn for brake lining. comprising twisted and intermingled fibres of asbestos and cotton in the proportion of five to one, a powdered mixture of iron oxide and magnesium silicate in the proportions of one to two coating the fibres of said asbestos and cotton, and brass wire twisted with said fibrous material for supporting the same,said magnesium silicate having a hardness of approximately one according to, the Mohs scale.

4. A brake lining comprising interwoven yarns, each yarn containingasbestos fibres coated with iron oxide in powdered form and a powdered carrier for said oxide, and a metallic filament for reinforcing the fibrous material.

5.A brake lining having a wearing surface consisting of a plurality ofindividual yarns, each yarn containing asbestos, cotton and powdered iron oxide.

6. A brake lining having a wearing surface consisting of a plurality of individual yarns, each yarn containing asbestos and powdered iron oxide, the amount of the iron oxide being by weight with reference to the asbestos between one-eighth of one percent and five percent.

7. A brake lining having a wearing surface "consisting of a plurality of individual yarns, each yarn containing asbestos and powdered iron oxide, the amount of the iron oxide being by 4% to 10%, metal 20% to 30%, iron oxide 0.1%

to 4%, magnesium silicate 0.2% to 8%, and an impregnant 10% to 20%.

10. A brake lininghaving a wearing surface consisting of aplurality of individual yarns, eachyarn containing asbestos 52%, cotton 8%, metal 26%, iron oxide 0.15%, magnesium silicate 0.3%,

WILLIAM NANFELDT. 

